Why is the amount of Net tax-empent interest on my state return less than the amount of interest on my US treasuries?

On the Interest Income Worksheet for my state return there is a section titled "Summary of Net Interest after Adjustments". Line 2 in that section is labeled "Net Arkansas tax-exempt interest and US obligations". The amount on that line is $741 less that the total amount of interest shown from US treasury obligations in the Interest Income worksheet. Does anyone know how this "Net tax-exempt interest is calculated"?

 

And it is NOT because on bond premium because I do not have any.